The following "parameters" are
read-only, and are determined when PostgreSQL is compiled or when it is
installed. As such, they have been excluded from the sample
postgresql.conf file. These options
report various aspects of PostgreSQL behavior that might be of
interest to certain applications, particularly administrative
front-ends.

block_size
(integer)

Reports the size of a disk block. It is determined by
the value of BLCKSZ when building
the server. The default value is 8192 bytes. The meaning of
some configuration variables (such as shared_buffers)
is influenced by block_size. See
Section 18.4 for
information.

integer_datetimes (boolean)

Reports whether PostgreSQL was built with support for
64-bit-integer dates and times. This can be disabled by
configuring with --disable-integer-datetimes when building
PostgreSQL. The default
value is on.

lc_collate
(string)

Reports the locale in which sorting of textual data is
done. See Section 22.1 for more
information. This value is determined when a database is
created.

lc_ctype (string)

Reports the locale that determines character
classifications. See Section 22.1
for more information. This value is determined when a
database is created. Ordinarily this will be the same as
lc_collate, but for special
applications it might be set differently.

max_function_args (integer)

Reports the maximum number of function arguments. It is
determined by the value of FUNC_MAX_ARGS when building the server. The
default value is 100 arguments.

max_identifier_length (integer)

Reports the maximum identifier length. It is determined
as one less than the value of NAMEDATALEN when building the server. The
default value of NAMEDATALEN is
64; therefore the default max_identifier_length is 63 bytes, which can
be less than 63 characters when using multibyte
encodings.

max_index_keys (integer)

Reports the maximum number of index keys. It is
determined by the value of INDEX_MAX_KEYS when building the server. The
default value is 32 keys.

segment_size
(integer)

Reports the number of blocks (pages) that can be stored
within a file segment. It is determined by the value of
RELSEG_SIZE when building the
server. The maximum size of a segment file in bytes is
equal to segment_size multiplied
by block_size; by default this is
1GB.

server_encoding (string)

Reports the database encoding (character set). It is
determined when the database is created. Ordinarily,
clients need only be concerned with the value of client_encoding.

server_version (string)

Reports the version number of the server. It is
determined by the value of PG_VERSION when building the server.

server_version_num (integer)

Reports the version number of the server as an integer.
It is determined by the value of PG_VERSION_NUM when building the server.

wal_block_size (integer)

Reports the size of a WAL disk block. It is determined
by the value of XLOG_BLCKSZ when
building the server. The default value is 8192 bytes.

wal_segment_size (integer)

Reports the number of blocks (pages) in a WAL segment
file. The total size of a WAL segment file in bytes is
equal to wal_segment_size
multiplied by wal_block_size; by
default this is 16MB. See Section 29.4 for more
information.